CN111162834B - Optical time domain reflectometer testing method and optical time domain reflectometer - Google Patents
Optical time domain reflectometer testing method and optical time domain reflectometer Download PDFInfo
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- CN111162834B CN111162834B CN201811318107.5A CN201811318107A CN111162834B CN 111162834 B CN111162834 B CN 111162834B CN 201811318107 A CN201811318107 A CN 201811318107A CN 111162834 B CN111162834 B CN 111162834B
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- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
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- H04B10/071—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using a reflected signal, e.g. using optical time domain reflectometers [OTDR]
Abstract
The embodiment of the invention provides an optical time domain reflectometer testing method and an optical time domain reflectometer, wherein the method comprises the following steps: triggering an Optical Time Domain Reflectometer (OTDR) to generate an initial optical signal according to the initial test parameters, and injecting the initial optical signal into an optical fiber for testing; in the testing process, the current testing distance of the initial optical signal is obtained through detection, if the current testing distance is judged to be not smaller than the critical testing distance, the OTDR is triggered to generate a modulated optical signal, and the modulated optical signal and the initial optical signal are jointly injected into the optical fiber to be tested. According to the embodiment of the invention, when the current testing distance is not less than the critical testing distance, the OTDR is triggered to generate the modulated optical signal to improve the optical power of the testing input end, so that the measuring range of the OTDR can be expanded, and the problems that the measuring range of the OTDR is fixed and the measuring track is submerged by noise are solved.
Description
Technical Field
The embodiment of the invention relates to the technical field of communication, in particular to an optical time domain reflectometer testing method and an optical time domain reflectometer.
Background
OTDR, an OpticaL Time Domain RefLectometer (OpticaL Time Domain RefLectometer), is mainly used in the field of OpticaL fiber communication, and has a high frequency of use. In practical application, the OTDR is mainly used for testing the optical fiber, and the optical path fault is quickly and accurately judged and positioned according to different waveforms displayed on a graphical interface. The principle is that under the control of an accurate clock circuit, a maintainer sets parameters according to an actual test scene, transmits a light pulse signal to an optical port, and then an OTDR continuously receives the light signal reflected from an optical fiber from the optical port according to a certain frequency. And respectively testing the loss of the optical fiber according to Rayleigh backscattering, calculating the distances of different fault points according to Fresnel reflection, and displaying the distances on a graphical interface. However, since the measurement range of the OTDR device in the prior art is fixed after shipment, the measurement range cannot be adjusted according to the field situation, and when the measurement range is out of the field situation, only the OTDR device in another measurement range can be replaced.
Disclosure of Invention
To solve the above problems, embodiments of the present invention provide an optical time domain reflectometer test method and an optical time domain reflectometer that overcome the above problems or at least partially solve the above problems.
According to a first aspect of the embodiments of the present invention, there is provided an optical time domain reflectometer testing method, including: triggering an Optical Time Domain Reflectometer (OTDR) to generate an initial optical signal according to the initial test parameters, and injecting the initial optical signal into an optical fiber for testing; in the testing process, the current testing distance of the initial optical signal is obtained through detection, if the current testing distance is judged to be not smaller than the critical testing distance, the OTDR is triggered to generate a modulated optical signal, and the modulated optical signal and the initial optical signal are jointly injected into the optical fiber to be tested.
According to a second aspect of embodiments of the present invention, there is provided an optical time domain reflectometer, comprising: a trigger and a modulation module; the trigger is used for detecting and obtaining the current test distance of the initial optical signal in the test process, and sending a trigger signal to the modulation module if the current test distance is judged to be not less than the critical test distance; the test is a test which is performed by triggering an Optical Time Domain Reflectometer (OTDR) to generate an initial optical signal and injecting the initial optical signal into an optical fiber in advance according to initial test parameters; the modulation module is used for generating a modulation optical signal according to the trigger signal and emitting the modulation optical signal and the initial optical signal into the optical fiber together for testing.
According to a third aspect of the embodiments of the present invention, there is provided an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, where the processor executes the computer program to implement the optical time domain reflectometer testing method as provided in any one of the various possible implementations of the first aspect.
According to a fourth aspect of embodiments of the present invention, there is provided a non-transitory computer-readable storage medium having stored thereon a computer program which, when executed by a processor, implements the optical time domain reflectometry test method as provided in any one of the various possible implementations of the first aspect.
According to the optical time domain reflectometer and the testing method thereof, provided by the embodiment of the invention, the current testing distance of the initial optical signal is obtained through detection in the testing process, the OTDR is triggered to generate the modulated optical signal when the current testing distance is confirmed to be not less than the critical testing distance, and the modulated optical signal and the initial optical signal are jointly injected into the optical fiber for testing. When the current test distance is not less than the critical test distance, the optical power of the test input end is improved by triggering the OTDR to generate a modulated optical signal, so that the measurement range of the OTDR can be expanded, and the problems that the measurement range of the OTDR is fixed and a measurement track is submerged by noise are solved; and triggering the OTDR to produce a modulated optical signal would only add minor hardware resources and cost.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from these without inventive effort.
Fig. 1 is a schematic flow chart of a testing method of an optical time domain reflectometer according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of an optical time domain reflectometer according to an embodiment of the present invention;
fig. 3 is a schematic physical structure diagram of an electronic device according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments, but not all embodiments, of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
For an optical time domain reflectometer, a chaos correlation method optical time domain reflectometer (COTDR) is researched in the prior art, fault location with space resolution of 6cm is realized by performing cross-correlation operation on reflected light of a reference light and a fault position, and test distance and test precision are improved. And in this study, the problem of attenuation of the optical fiber was not considered. In the prior art, a high-speed optical time domain reflectometer is also studied, wherein the reflectometer uses a gray complementary code as a detection signal, and performs correlation operation on an echo signal and the gray complementary code, so as to quickly position a breakpoint in an optical fiber. However, since only the autocorrelation technique is adopted in the design, the signal-to-noise ratio is improved by increasing the number of symbol bits, but the consumption of hardware resources is also increased sharply due to the increase of the number of symbol bits.
Therefore, the prior art has at least the following drawbacks: 1. the dynamic measurement range is fixed and is smaller; the method is influenced by noise, the far end which can be actually measured cannot be measured, the measurement track is submerged in the noise, and the measured track fluctuates greatly sometimes; in the improved technology, the added hardware resource cost is higher, and the improved mechanism does not effectively take the measurement range and the signal-to-noise ratio into consideration.
Based on this, the embodiment of the invention provides a method for testing an optical time domain reflectometer. Referring to fig. 1, the method includes:
101. triggering the OTDR to generate an initial optical signal according to the initial test parameters, and injecting the initial optical signal into the optical fiber for testing.
Before step 101, a conventional OTDR may be modified, for example, as shown in fig. 2, a modified modulation functional module may be added, so that the modified OTDR can generate a modulated optical signal. It should be noted that the specific modification shown in fig. 2 is only one possible modification, and the specific modification is not limited in the embodiment of the present invention, and only the OTDR can generate the modulated optical signal as needed. In step 101, before performing a test using the OTDR, test parameters of the OTDR need to be configured, where the test parameters include: the measurement range, the measurement wavelength, the pulse width, the measurement time, the refractive index and other parameters are not limited in the embodiment of the present invention. The use of initial test parameters to trigger the OTDR for testing may be understood as a conventional OTDR test, that is, only a signal source laser is triggered, and an initial optical signal generated by the laser is injected into an optical fiber access port (i.e., an optical fiber injection end) through a coupler, so as to enter an optical fiber to be tested, thereby testing the optical fiber to be tested.
102. In the testing process, the current testing distance of the initial optical signal is obtained through detection, if the current testing distance is judged to be not smaller than the critical testing distance, the OTDR is triggered to generate a modulated optical signal, and the modulated optical signal and the initial optical signal are jointly injected into the optical fiber to be tested.
Specifically, the initial optical signal is launched into the optical fiber in step 101, and then enters the testing process. In the test process, fresnel reflection occurs after an initial optical signal enters the optical fiber, and then, the distance between the fresnel reflection position and the injection end of the optical fiber is the current test distance, which can also be understood as the farthest distance in the optical fiber that the initial optical signal can reach. In other words, the current test distance is the distance between the initial optical signal where the fresnel reflection occurs and the injection end of the optical fiber. After the current testing distance is obtained through detection, the current testing distance is compared with the critical testing distance, if the current testing distance is not smaller than the critical testing distance, namely the current testing distance is larger than or equal to the critical testing distance, it is indicated that an optical signal (namely an initial optical signal) which is currently input into the optical fiber to be tested is small, the measurement noise is large at the moment, and the far end of the optical fiber is difficult to accurately measure. The OTDR may thus be triggered to generate a modulated optical signal and inject the modulated optical signal and the original optical signal together into the optical fiber for testing. Compared with the initial optical signal, the modulated optical signal is added, so that the optical power of the optical fiber input end is improved, the test distance of the optical signal input into the optical fiber can be increased, and the test range of the OTDR is increased.
In the method provided by the embodiment of the invention, the current test distance of the initial optical signal is obtained by detection in the test process, the OTDR is triggered to generate the modulated optical signal when the current test distance is not smaller than the critical test distance, and the modulated optical signal and the initial optical signal are jointly injected into the optical fiber for testing. When the current test distance is not less than the critical test distance, the optical power of the test input end is improved by triggering the OTDR to generate a modulated optical signal, so that the measurement range of the OTDR can be expanded, and the problems that the measurement range of the OTDR is fixed and a measurement track is submerged by noise are solved; and triggering the OTDR to produce a modulated optical signal would only add minor hardware resources and cost.
Based on the content of the foregoing embodiment, as an alternative embodiment, the detecting a current test distance of obtaining the initial optical signal includes:
wherein L is the current test distance, alpha is the attenuation constant of the optical fiber, and P0For peak power injected into the fiber, RFIs the Fresnel reflection coefficient, PFAnd (L) is the optical power of Fresnel reflection measured at the injection end of the optical fiber.
Specifically, the current test distance is obtained specifically as follows:
according to the fresnel reflection principle, the fresnel reflection light power:
PF＝RF×P0formula (1)
Optical power at distance L (i.e. at fresnel reflection):
P(L)＝P0×e-αL/10formula (2)
Therefore, for Fresnel reflection light from the fiber L meters away from the light source, the optical power P measured at the injection end of the fiberF(L) is:
PF(L)＝RF×P0×e-2αL/10formula (3)
Wherein α is the attenuation constant of the optical fiber, P0For peak power injected into the fiber, RFAnd L is the distance from the Fresnel reflection position to the light injection end.
Thus, the dynamically detected current test distance L is:
definition of RFThe reflection coefficient is:
where n is the refractive index of the fiber and θ is the angle of incidence.
Therefore, the current test distance L can be calculated according to the fresnel reflected light power measured by the OTDR.
Based on the content of the foregoing embodiments, before judging and knowing that the current test distance is not less than the critical test distance, as an optional embodiment, a method for determining the critical test distance is provided, which includes but is not limited to: and obtaining the absorption attenuation at the Fresnel reflection part, wherein the distance between the Fresnel reflection part and the optical fiber injection end is the current test distance, and determining the critical test distance according to the absorption attenuation.
As an alternative example, the absorption decay is:
PA(L)＝P0-P(L)-PF(L)-PR(L)
wherein the content of the first and second substances,
P(L)＝P0×e-αL/10
PF(L)＝RF×P0×e-2αL/10
PR(L)＝γ(L)×P(L)×e-αL/10
in the formula, PA(L) is absorption decay, P0For the peak power injected into the fiber, α is the fiber attenuation constant, RFFor the Fresnel reflection coefficient, L is the current test distance, n is the fiber refractive index, θ is the angle of incidence, V is the group velocity of light in the fiber core, αRIs the Rayleigh scattering coefficient, S is the ratio of the back-scattered power to the total Rayleigh scattered power, and γ (L) is the Rayleigh scattering factor.
Specifically, the absorption decay PA(L) is defined as:
PA(L)＝P0-P(L)-PF(L)-PR(L) formula (6)
After the light pulse is incident on the optical fiber, the optical power p (L) at the distance L is:
P(L)＝P0×e-αL/10formula (7)
Wherein, alpha is attenuation coefficient, P0Is the peak optical power launched into the fiber.
Due to the effect of rayleigh scattering, a part of light at L returns to the optical cable detector, and the rayleigh backscattered light power at L measured by the detector is:
PR(L)＝γ(L)×P(L)×e-αL/10formula (8)
Define γ (L) as the rayleigh scattering factor:
where V represents the group velocity of light in the core, αRExpressing Rayleigh scattering coefficient, S expressing backThe ratio of the total scattered power to the Rayleigh scattered power, T, is the pulse width.
Absorption decay P provided by the embodiment of the inventionA(L) by defining the absorption decay PAAnd (L) and a calculation mode, wherein the sum of power attenuation except the light power at the position L, the received Rayleigh backscattering power and the Fresnel reflection power is uniformly defined as absorption attenuation. In this definition, the effective power that can be detected by OTDR is taken into account, and a reasonable decision condition is further proposed, that is, when the absorption loss reaches the maximum, the absorption loss extremal distance L is obtainedAThereby triggering the improved modulation module. Through the judgment mechanism, the outstanding problem that the measurement track is submerged by noise is well solved.
After the above absorption decay is defined, the critical distance is determined based on the absorption decay. Based on the content of the above embodiment, as an optional embodiment, the critical test distance is:
L0＝min(LM，LA)
wherein the content of the first and second substances,
in the formula, L0Is a critical test distance, LMFor theoretical monitoring of the longest distance, L, of OTDRAIs the absorption decay extremum distance; p is the dynamic range of the OTDR input power, DcFor access loss, DfIs the average attenuation coefficient of the cable, DsIs the average attenuation coefficient, M, of the optical fiber splicecFor optical cable lines rich, MaThe OTDR test precision is more than the standard.
Specifically, the critical distance L0The calculation method is as follows:
L0＝min(LM，LA) Formula (10)
Definition of LAFor the absorption loss extremum distance, the meaning of this distance is: and when the absorption attenuation reaches the maximum, measuring the distance from the light injection end, namely measuring the distance between the position reached by the initial light signal and the light injection end when the absorption attenuation reaches the maximum.
In the case of a single signal source, the theoretical monitoring of the OTDR is carried out over a maximum distance LMComprises the following steps:
p: the dynamic range of the OTDR module input power, provided by the system provider;
Dc: the access loss refers to the sum of the intervention of devices such as OTDR, optical switch, WDM, filter and the like;
Df: the average attenuation coefficient of the optical cable is in db/km;
Ds: the average attenuation coefficient of the optical fiber connector is in db/km;
Mc: the optical cable line richness, unit db;
Ma: the OTDR test accuracy is rich in degrees, in db.
Absorption loss limit distance LAThe calculation process of (2) is as follows:
expanding equation (6) yields the following expression:
PA(L)＝P0-P0×e-αL/10-RF×P0×e-2αL/10-γ(L)×P0×e-2αL/10formula (12)
Assuming that the fiber is uniform, i.e., γ (0) ═ γ (L), we obtain:
PA(L)＝-[RF+γ(0)]×P0×e-2αL/10-P0×e-αL/10+P0formula (13)
For equation (12), L is derived:
when in use
At this time, the absorption decay reached the maximum, and the following were obtained:
thereby obtaining the absorption loss extreme value distance L when the absorption loss reaches the maximumAComprises the following steps:
LAl formula (16)
Based on the content of the foregoing embodiment, after detecting the current test distance reached by obtaining the initial optical signal, as an optional embodiment, the method further includes: if the current testing distance is smaller than the critical testing distance, resetting the initial testing parameters according to a first testing result graph output by the OTDR to obtain target testing parameters; triggering the OTDR to generate an initial optical signal according to the target test parameter, and injecting the initial optical signal into the optical fiber to perform the test again, so that a second test result graph output by the OTDR is clearer compared with a first test result graph. Specifically, if the current test distance is smaller than the critical test distance, it indicates that the test distance when the initial optical signal is used for testing is within the test range, and the OTDR does not need to be triggered to generate the modulated optical signal. Therefore, the test parameters are only needed to be reconfigured according to the first test result, and the initial optical signal is used for carrying out the test again, so that the graph output result is more visual and clear.
Based on the content of the foregoing embodiment, another embodiment is provided below to explain the optical time domain reflectometer testing method provided by the foregoing embodiment, where the embodiment specifically includes the following steps:
step 1: an emission device of the OTDR is improved, a modulation device is added, the initial OTDR is in a non-modulation light source state, and only a signal source laser is triggered, as shown in FIG. 2;
step 2: according to the illustration in fig. 2, various test parameters under the current situation are reasonably set in advance: measuring range, measuring wavelength, pulse width, measuring time, refractive index and other parameters;
and step 3: in the test process, the distance L reached by the current light is dynamically detected, and the absorption attenuation P at the current distance L from the test end is analyzed and calculated in real timeA(L)；
And 4, step 4: if the distance L tested currently is less than the critical distance L0If yes, executing step 5; if L is greater than or equal to L0If yes, executing step 6;
and 5: resetting each OTDR performance parameter in the step 2 according to the test result, and retesting so that the graph output result is more visual and clear without triggering a modulation signal source;
step 6: according to fig. 2, the modified modulation function module of the OTDR is triggered, and the laser source generates a modulation signal through the modulator, and is injected into the launch port through the coupler, and the optical fiber is tested.
Based on the content of the foregoing embodiments, an embodiment of the present invention provides an optical time domain reflectometer, where the optical time domain reflectometer is used to execute the optical time domain reflectometer testing method in the foregoing method embodiments. Referring to fig. 2, the optical time domain reflectometer includes: a trigger and a modulation module; the trigger is used for detecting and obtaining the current test distance of the initial optical signal in the test process, and sending a trigger signal to the modulation module if the current test distance is judged to be not less than the critical test distance; the test is a test which is performed by triggering an Optical Time Domain Reflectometer (OTDR) to generate an initial optical signal and injecting the initial optical signal into an optical fiber in advance according to initial test parameters; the modulation module is used for generating a modulation optical signal according to the trigger signal and emitting the modulation optical signal and the initial optical signal into the optical fiber together for testing.
Before the OTDR is used for testing, test parameters of the OTDR need to be configured, where the test parameters include: the measurement range, the measurement wavelength, the pulse width, the measurement time, the refractive index and other parameters are not limited in the embodiment of the present invention. The use of initial test parameters to trigger the OTDR for testing may be understood as a conventional OTDR test, that is, only a signal source laser is triggered, and an initial optical signal generated by the laser is injected into an optical fiber access port (i.e., an optical fiber injection end) through a coupler, so as to enter an optical fiber to be tested, thereby testing the optical fiber to be tested.
In the test process, fresnel reflection occurs after an initial optical signal enters the optical fiber, and then, the distance between the fresnel reflection position and the injection end of the optical fiber is the current test distance, which can also be understood as the farthest distance in the optical fiber that the initial optical signal can reach. In other words, the current test distance is the distance between the initial optical signal where the fresnel reflection occurs and the injection end of the optical fiber. After the trigger detects and obtains the current testing distance, the current testing distance is compared with the critical testing distance, if the current testing distance is not smaller than the critical testing distance, namely the current testing distance is larger than or equal to the critical testing distance, it indicates that the optical signal (namely the initial optical signal) currently input into the optical fiber for testing is small, the measurement noise is large at the moment, and the remote end of the optical fiber is difficult to accurately measure. Therefore, the trigger can trigger the modulation module to generate a modulated optical signal, and the modulated optical signal and the initial optical signal are injected into the optical fiber together for testing. Compared with the initial optical signal, the modulated optical signal is added, so that the optical power of the optical fiber input end is improved, the test distance of the optical signal input into the optical fiber can be increased, and the test range of the OTDR is increased.
In the optical time domain reflectometer provided by the embodiment of the invention, the current test distance of the initial optical signal is obtained through detection in the test process, the OTDR is triggered to generate the modulated optical signal when the current test distance is confirmed to be not less than the critical test distance, and the modulated optical signal and the initial optical signal are jointly injected into the optical fiber for testing. When the current test distance is not less than the critical test distance, the optical power of the test input end is improved by triggering the OTDR to generate a modulated optical signal, so that the measurement range of the OTDR can be expanded, and the problems that the measurement range of the OTDR is fixed and a measurement track is submerged by noise are solved; and triggering the OTDR to produce a modulated optical signal would only add minor hardware resources and cost.
Based on the content of the foregoing embodiments, as an alternative embodiment, the modulation module includes: a laser, a modulator, a modulated light source and a demodulator; the input end of the trigger is connected with the pulse generator, the output end of the trigger is respectively connected with the input ends of the laser and the modulation light source, the output end of the laser and the output end of the modulation light source are connected with the input end of the modulator, the output end of the modulator is connected with the input end of the coupler, and the arithmetic unit is connected with the A/D converter through the demodulator.
Specifically, based on the modulation module, the test process is as follows: firstly, triggering a laser to generate an initial optical signal according to initial test parameters, and enabling the initial optical signal to enter an optical fiber access port through a modulator and a coupler in sequence so as to test an optical fiber. Then, after the trigger detects and obtains the current testing distance, the current testing distance is compared with the critical testing distance, and if the current testing distance is not smaller than the critical testing distance, the trigger wants to modulate the light source to send a trigger signal; the modulation light source receives the trigger signal and then generates a modulation light signal, the modulation light signal enters the modulator, and the modulation light signal and the initial light signal are emitted into the optical fiber together through the coupler for testing after being modulated.
Compared with the prior art, the optical time domain reflectometer and the testing method thereof have the following advantages that:
1. the embodiment of the invention improves the modulation device (namely the trigger and the modulation module) of the OTDR. The existing OTDR equipment measurement range is fixed after leaving a factory, the measurement range cannot be adjusted according to the field condition, and only a tester can be replaced when the measurement range is exceeded. In view of this, the embodiment of the present invention improves the modulation apparatus of the OTDR, and determines whether to trigger the improved modulation function module by dynamically detecting the current measurement distance, thereby improving the measurement range and the signal-to-noise ratio.
2. The embodiment of the invention provides absorption attenuation PAThe calculation method of (L). By definition of the absorption decay PAAnd (L) and a calculation mode, wherein the sum of power attenuation except the light power at the position L, the received Rayleigh backscattering power and the Fresnel reflection power is uniformly defined as absorption attenuation. In this definition, the effective power that can be detected by the OTDR is taken into account, and it is further proposed thatObtaining the distance L of the extreme value of the absorption loss under a reasonable judgment condition, namely when the absorption loss reaches the maximumAThereby triggering the improved modulation module. Through the judgment mechanism, the outstanding problem that the measurement track is submerged by noise is well solved.
An embodiment of the present invention provides an electronic device, as shown in fig. 3, the electronic device includes: a processor (processor)301, a communication Interface (communication Interface)302, a memory (memory)303 and a communication bus 304, wherein the processor 301, the communication Interface 302 and the memory 303 complete communication with each other through the communication bus 304. The processor 301 may call a computer program on the memory 303 and operable on the processor 301 to execute the optical time domain reflectometer testing method provided by the above embodiments, for example, including: triggering an Optical Time Domain Reflectometer (OTDR) to generate an initial optical signal according to the initial test parameters, and injecting the initial optical signal into an optical fiber for testing; in the testing process, the current testing distance of the initial optical signal is obtained through detection, if the current testing distance is judged to be not smaller than the critical testing distance, the OTDR is triggered to generate a modulated optical signal, and the modulated optical signal and the initial optical signal are jointly injected into the optical fiber to be tested.
In addition, the logic instructions in the memory 303 may be implemented in the form of software functional units and stored in a computer readable storage medium when the logic instructions are sold or used as independent products. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
Embodiments of the present invention further provide a non-transitory computer-readable storage medium, on which a computer program is stored, where the computer program is implemented to perform the optical time domain reflectometer testing method provided in the foregoing embodiments when executed by a processor, for example, the method includes: triggering an Optical Time Domain Reflectometer (OTDR) to generate an initial optical signal according to the initial test parameters, and injecting the initial optical signal into an optical fiber for testing; in the testing process, the current testing distance of the initial optical signal is obtained through detection, if the current testing distance is judged to be not smaller than the critical testing distance, the OTDR is triggered to generate a modulated optical signal, and the modulated optical signal and the initial optical signal are jointly injected into the optical fiber to be tested.
The above-described embodiments of the electronic device and the like are merely illustrative, and units illustrated as separate components may or may not be physically separate, and components displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium, such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute the various embodiments or some parts of the methods of the embodiments.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (9)
1. An optical time domain reflectometer test method is characterized by comprising the following steps:
triggering an Optical Time Domain Reflectometer (OTDR) to generate an initial optical signal according to initial test parameters, and injecting the initial optical signal into an optical fiber for testing;
in the testing process, detecting and obtaining the current testing distance of the initial optical signal, if judging and obtaining that the current testing distance is not smaller than the critical testing distance, triggering OTDR to generate a modulated optical signal, and injecting the modulated optical signal and the initial optical signal into the optical fiber together for testing;
the detecting obtains a current test distance of the initial optical signal, including:
wherein L is the current test distance, alpha is the attenuation constant of the optical fiber, and P0For peak power injected into the fiber, RFIs the Fresnel reflection coefficient, PF(L) is the Fresnel reflected light power measured at the injection end of the optical fiber;
the expression for the critical test distance is as follows:
L0＝min(LM，LA)
wherein L is0Is a critical test distance, LMFor theoretical monitoring of the longest distance, L, of OTDRATo absorb attenuation extrema distances.
2. The method of claim 1, wherein before the determining that the current testing distance is not less than the critical testing distance, the method further comprises:
and acquiring the absorption attenuation of the Fresnel reflection part, wherein the distance between the Fresnel reflection part and the optical fiber injection end is the current test distance, and determining the critical test distance according to the absorption attenuation.
3. The method of claim 2, wherein the absorption decay is:
PA(L)＝P0-P(L)-PF(L)-PR(L)
wherein the content of the first and second substances,
P(L)＝P0×e-αL/10
PF(L)＝RF×P0×e-2αL/10
PR(L)＝γ(L)×P(L)×e-αL/10
in the formula, PA(L) is absorption decay, P0For the peak power injected into the fiber, α is the fiber attenuation constant, RFFor the Fresnel reflection coefficient, L is the current test distance, n is the fiber refractive index, θ is the angle of incidence, V is the group velocity of light in the fiber core, αRIs the Rayleigh scattering coefficient, S is the ratio of the back-scattered power to the total Rayleigh scattered power, γ (L) is the Rayleigh scattering factor, and T is the pulse width.
4. The method of claim 3,
where P is the dynamic range of the OTDR input power, DcFor access loss, DfIs the average attenuation coefficient of the cable, DsIs the average attenuation coefficient, M, of the optical fiber splicecFor optical cable lines rich, MaFor OTDR test accuracy richness, γ (0) is the initial Rayleigh scattering factor.
5. The method of claim 1, wherein after the detecting obtains the current test distance reached by the initial optical signal, further comprising:
if the current testing distance is judged to be smaller than the critical testing distance, resetting the initial testing parameters according to a first testing result graph output by the OTDR to obtain target testing parameters;
triggering the OTDR to generate the initial optical signal according to the target test parameter, and injecting the initial optical signal into the optical fiber to perform testing again, so that a second test result graph output by the OTDR is clearer compared with the first test result graph.
6. An optical time domain reflectometer, comprising: a trigger and a modulation module;
the trigger is used for detecting and obtaining the current test distance of the initial optical signal in the test process, and sending a trigger signal to the modulation module if the current test distance is judged and obtained to be not less than the critical test distance; the test is a test which is performed by triggering an Optical Time Domain Reflectometer (OTDR) to generate an initial optical signal in advance according to initial test parameters and injecting the initial optical signal into an optical fiber;
the modulation module is used for generating a modulation optical signal according to the trigger signal and emitting the modulation optical signal and the initial optical signal into the optical fiber together for testing;
the detecting obtains a current test distance of the initial optical signal, including:
wherein L is the current test distance, alpha is the attenuation constant of the optical fiber, and P0For peak power injected into the fiber, RFIs the Fresnel reflection coefficient, PF(L) is the Fresnel reflected light power measured at the injection end of the optical fiber;
the expression for the critical test distance is as follows:
L0＝min(LM，LA)
wherein L is0Is a critical test distance, LMFor theoretical monitoring of the longest distance, L, of OTDRATo absorb attenuation extrema distances.
7. The optical time domain reflectometer as in claim 6, wherein the modulation module comprises: a laser, a modulator, a modulated light source and a demodulator;
the input end of the trigger is connected with the pulse generator, the output end of the trigger is respectively connected with the laser and the input end of the modulation light source, the output end of the laser and the output end of the modulation light source are connected with the input end of the modulator, the output end of the modulator is connected with the input end of the coupler, and the arithmetic unit is connected with the A/D converter through the demodulator.
8. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the steps of the optical time domain reflectometry test method according to any of claims 1 to 5 are implemented when the program is executed by the processor.
9. A non-transitory computer readable storage medium having stored thereon a computer program, wherein the computer program, when executed by a processor, implements the steps of the optical time domain reflectometry test method according to any of claims 1 to 5.
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